The principal effect of HBOT is increasing the solubility of oxygen in plasma to a level sufficient to support tissues with minimal oxygen supply carried on by hemoglobin. Transport of oxygen to mitochondria, the main sites of oxygen utilization within each individual cell, occurs by diffusion, via a stepwise decrease in the driving oxygen pressure gradient. Diffusion oxygen gradient is a vector indicating the direction of the greatest rate of change between oxygen dissolved in the blood and oxygen within the cell/entire tissue. As a whole, breathing oxygen under hyperbaric conditions has been shown to be a potent means of increasing arterial oxygen tension, as well as tissue oxygen tension. For example, at 2 absolute atmospheres (ATA), plasma O2 tension rises above 1110 mmHg, whereas at normal environmental conditions, i.e. at the sea level, it reaches only 98 mmHg. As can be concluded, hyperbaric conditions can provide about a ten-fold increase in the amounts of O2 reaching the hypoxic cardiac tissue. HBO therapy is well tolerated and has been considered safe when used according to the standard protocols, with oxygen pressure not exceeding 3 ATA and treatment sessions limited to a maximum of 120 min.